** Description changed:
[Impact]
- kprobes are not available on arm64, a useful debug feature available on all
other supported Ubuntu architectures. I failed to catch this when I reviewed
the yakkety config because I was just looking for regressions vs. enabling new
features (arm64/kprobes is new in 4.8).
+ kprobes is currently enabled for all Ubuntu architectures except arm64. This
excludes a useful debug feature, which is required by certain userspace
provided by Ubuntu, such as perf's probe command. I failed to notice this in my
yakkety config review because it is a new feature in v4.8.
[Test Case]
- sudo perf probe schedule
- sudo perf record -e probe:schedule -aR sleep 1
+ = Failure case =
+ ubuntu@arm64:~$ sudo perf probe schedule
+ kprobe_events file does not exist - please rebuild kernel with
CONFIG_KPROBE_EVENTS.
+ Error: Failed to add events.
+
+ = Success case =
+ ubuntu@arm64:~$ sudo perf probe schedule
+ Added new event:
+ probe:schedule (on schedule)
+
+ You can now use it in all perf tools, such as:
+
+ perf record -e probe:schedule -aR sleep 1
+
+ ubuntu@arm64:~$ sudo perf record -e probe:schedule -aR sleep 1
+ [ perf record: Woken up 1 times to write data ]
+ [ perf record: Captured and wrote 0.185 MB perf.data (61 samples) ]
[Regression Risk]
The proposed fix enables a config for an already-upstream feature, so
regressions will have upstream support. The config change mostly results in
building new code vs. modifying existing code. The notable exception is that
arm64's notify_page_fault() will now get code to call kprobe_fault_handler() -
but only in the case that this newly enabled feature is being used (if
kprobe_running()).

Advertising

--
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1634271
Title:
arm64: kprobes disabled
Status in linux package in Ubuntu:
In Progress
Bug description:
[Impact]
kprobes is currently enabled for all Ubuntu architectures except arm64. This
excludes a useful debug feature, which is required by certain userspace
provided by Ubuntu, such as perf's probe command. I failed to notice this in my
yakkety config review because it is a new feature in v4.8.
[Test Case]
= Failure case =
ubuntu@arm64:~$ sudo perf probe schedule
kprobe_events file does not exist - please rebuild kernel with
CONFIG_KPROBE_EVENTS.
Error: Failed to add events.
= Success case =
ubuntu@arm64:~$ sudo perf probe schedule
Added new event:
probe:schedule (on schedule)
You can now use it in all perf tools, such as:
perf record -e probe:schedule -aR sleep 1
ubuntu@arm64:~$ sudo perf record -e probe:schedule -aR sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.185 MB perf.data (61 samples) ]
[Regression Risk]
The proposed fix enables a config for an already-upstream feature, so
regressions will have upstream support. The config change mostly results in
building new code vs. modifying existing code. The notable exception is that
arm64's notify_page_fault() will now get code to call kprobe_fault_handler() -
but only in the case that this newly enabled feature is being used (if
kprobe_running()).
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1634271/+subscriptions
--
Mailing list: https://launchpad.net/~kernel-packages
Post to : kernel-packages@lists.launchpad.net
Unsubscribe : https://launchpad.net/~kernel-packages
More help : https://help.launchpad.net/ListHelp